Add nil guard to syslog sink add_record

Prevent errors when @syslog is nil (e.g., when the sink hasn't been
opened). This allows the sink to gracefully handle uninitialized state
instead of raising: "undefined method `log' for nil"

Also remove the singleton reset from syslog_spec after hook since the
nil guard makes it unnecessary and it was interfering with other tests
that mock the singleton with exact call expectations.

Author: johha

lib/steno/sink/syslog.rb

@@ -35,6 +35,7 @@ def open(identity)
 
   def add_record(record)
     return if record.log_level == :off
+    return unless @syslog
 
     record = truncate_record(record)
     msg = @codec.encode_record(record)

spec/spec_helper.rb

@@ -207,8 +207,14 @@
 
     rspec_config.after do
       # Reset the Syslog sink singleton to prevent mock leakage between tests
-      if defined?(Steno::Sink::Syslog)
-        Steno::Sink::Syslog.instance.instance_variable_set(:@syslog, nil)
+      # Skip for tests that mock the singleton itself (tagged with skip_syslog_reset)
+      if !RSpec.current_example.metadata[:skip_syslog_reset] && defined?(Steno::Sink::Syslog)
+        begin
+          instance = Steno::Sink::Syslog.instance
+          instance.instance_variable_set(:@syslog, nil) if instance.respond_to?(:instance_variable_set)
+        rescue StandardError
+          # Ignore any errors - the test may be managing the singleton itself
+        end
       end
     end
 

spec/unit/lib/steno/unit/config_spec.rb

@@ -4,7 +4,7 @@
 require 'steno'
 
 RSpec.describe Steno::Config do
-  describe '.from_hash' do
+  describe '.from_hash', :skip_syslog_reset do
     before do
       @log_path = 'some_file'
 
@@ -113,7 +113,7 @@
       expect(config.sinks[0]).to eq(mock_sink)
     end
 
-    it "adds a syslog sink if the 'syslog' key is specified" do
+    it "adds a syslog sink if the 'syslog' key is specified", :skip_syslog_reset do
       write_config(@config_path, { 'syslog' => 'test' })
       mock_sink = double('sink')
       expect(mock_sink).to receive(:open).with('test')

spec/unit/lib/steno/unit/sink/syslog_spec.rb

@@ -17,8 +17,6 @@
   describe '#add_record' do
     after do
       Syslog.close if Syslog.opened?
-      # Reset the singleton's syslog instance to prevent mock leakage between tests
-      described_class.instance.instance_variable_set(:@syslog, nil)
     end
 
     it 'appends an encoded record with the correct priority' do